Connection structure for glued laminated timber

ABSTRACT

A glulam construction method suitable for relatively small-sized wooden buildings is disclosed. Each joint metal has its plate portion and pipe portion joined in a racket-like shape. At an end of a column, a slit is formed to open at a column end surface and to extend in a column width direction. At an abutment part in a beam abutting on the column end surface, mortises penetrating in a beam depth direction are formed at two positions appropriately spaced from each other in a span direction. Each joint metal has its pipe portion fitted in the corresponding mortise and has its plate portion fitted in the slit of the column. The joint metals are fixed in the column and the beam by drift pins or bolts and thereby establish rigid connection therebetween.

TECHNICAL FIELD

The present invention relates to a connection structure for glued laminated timber (“glulam”).

BACKGROUND ART

Basic construction methods for wooden buildings include the conventional wooden framework construction method (post and beam construction method), the two-by-four method, the log construction method, etc. These construction methods have been precisely and specifically prescribed by the Building Standard Law of Japan, the Enforcement Order of the Building Standard Law of Japan, ministerial announcements by the Ministry of Construction, etc., in terms of specifications of structural members such as species, size, position, and manner of connection. Construction methods for wooden buildings further include the prefabricated construction method and the panel construction method, according to which structural load-bearing elements such as floor framing and wall framing are produced collectively in advance in a factory and assembled on site. Among these construction methods, those based on the wooden framework construction method and the two-by-four method have been subjected to prescriptive provisions under the regulations of the Building Standard Law of Japan, etc., but those involving legally unanticipated special structures are required to obtain individual approvals by the Minister of Construction.

To apply the lessons learned from the Great Hanshin-Awaji Earthquake and to relax regulations, the Building Standard Law of Japan was significantly revised in 2000, with major changes in regulations regarding structural performance and fire-prevention performance of buildings. The legal revision has legislated the mechanism that is flexibly applicable to new construction methods and new materials by introducing “performance-based provisions” that indicate required performance of buildings, instead of the previous “prescriptive provisions”. For effective enforcement of the performance-based provisions, this legal revision also introduced some subsystems such as new approval systems by the Minister of Construction (Minister of Land, Infrastructure, Transport and Tourism), type conformity approval system, and certification system of the manufacturer of the certified model member, etc.

SUMMARY OF INVENTION Technical Problem

The above-mentioned revisions of the Building Standard Law of Japan and its relevant laws/regulations have extended the range of construction methods and types of materials applicable to wooden houses.

As a specific example, let us mention a building that uses structural glued laminated timber for a part of its building frame. Under the former Building Standard Law, the prescriptive provisions gave standards of specifications for a wooden building using large dimension (i.e., large cross-section) glued laminated timber, but did not permit, in principle, any construction methods using medium or small dimension (i.e., medium or small cross-section) glued laminated timber as building frames of mass-production prefabricated houses and other like buildings. However, now that various regulations including dimensional restrictions on the cross-section of structural members are relaxed by the above-mentioned legal revision, construction methods using medium or small dimension glued laminated timber in building frames may be able to receive type conformity approval and certification of the manufacturer of the certified model member, etc. by satisfying prescribed criteria.

Glued laminated timber, made of laminas laminated and glued on top of each other, not only has greater strength and dimensional stability than natural timber, but also has high design property and shaping/modeling property. Besides, glued laminated timber significantly contributes to effective use of forest resources. Such advantages have been pushing up the demand for glued laminated timber. There is also a growing demand for development of a novel wooden house construction method that makes full use of the advantages of glued laminated timber.

The present invention is made in view of these circumstances, and aims to provide a novel construction method suitable for a relatively small-sized wooden buildings such as residential houses, specifically, to provide a glued laminated timber construction method that uses medium or small dimension structural glued laminated timber in a building frame based on a rigid frame structure (Rahmen structure). A problem to be solved by the present invention is to disclose a specific configuration of a connection structure between a column and a beam made of glued laminated timber, as one of the load-bearing elements in the glued laminated timber construction method.

Solution to Problem

To achieve the above object, the present invention provides a connection structure for glued laminated timber, in which a column and a beam made of medium or small dimension glued laminated timber are rigidly connected by a pair of joint metals such that the beam is connected on top of the column. Each of the joint metals includes a plate portion and a pipe portion that are joined together in a racket-like shape, each of the plate portion and the pipe portion having a fixing hole for a drift pin or a bolt. The column is provided with a slit at an end thereof, the slit opening at a column end surface and extending in a column width direction. The beam is provided with mortises at an abutment part thereof that abuts on the column end surface, the mortises penetrating in a beam depth direction and arranged at two positions that are appropriately spaced from each other in a span direction. The pair of joint metals is fixed in the column and the beam by having the pipe portion of each joint metal fitted in corresponding one of the mortises and by having the plate portion of each joint metal being fitted in the slit of the column, and thereby establishes rigid connection between the column and the beam.

In the connection structure according to the present invention, an auxiliary metal having a first end and a second end may be arranged in between the pair of joint metals. The first end of the auxiliary metal may be fixed in the column by a drift pin or a bolt, and the second end of the auxiliary metal may be fixed in the beam by a drift pin or a bolt.

Further, each of the joint metals may include a plurality of pipe portions per plate portion, and the pipe portions may extend parallel to each other from a peripheral side of the plate portion.

Further, a flat connector plate may be connected to the pipe portion of at least one of the pair of joint metals, on a top surface side of the beam that is connected to a lower-story column by the pair of joint metals. An upper-story column may be erected on the beam by having the connector plate fitted in a slit formed at a lower end of the upper-story column.

Note that the glued laminated timber is classified into structural glued laminated timber or glued laminated timber for fixtures, and that the glued laminated timber construction method according to the present invention uses structural glued laminated timber. The standards for structural glued laminated timber is newly established in “JAS for structural glued laminated timber” under Public Notice of the Ministry of Agriculture, Forestry and Fisheries No. 111 of 1996, which integrates prior standards “the standard for structural glued laminated timber” and “JAS for structural large dimension glued laminated timber”. According to the new standard, the term “large dimension glued laminated timber” refers to glued laminated timber whose cross section has shorter sides of 15 cm or greater and an area of 300 cm² or greater. The term “medium dimension glued laminated timber” refers to glued laminated timber whose cross section has shorter sides of 7.5 cm or greater and longer sides of 15 cm or greater, except the large dimension glued laminated timber. The term “small dimension glued laminated timber” refers to glued laminated timber whose cross section has shorter sides of less than 7.5 cm or longer sides of less than 15 cm. The present invention relies on this standard for the definition of the cross sectional size of the structural glued laminated timber.

Advantageous Effects of Invention

The connection structure for glued laminated timber according to the present invention provides rigid connection between a column and a beam made of medium or small dimension glued laminated timber, using a pair of joint metals each having a plate portion and a pipe portion, such that the beam is connected on top of the column. As a result, a building frame constructed by combining such rigid connections has greater strength and higher rigidity than the one constructed by the common conventional wooden framework construction method (post and beam construction method) using natural timber. Particularly in terms of rigidity, the connection structure according to the present invention shows much higher initial rigidity at the connection than the conventional structure because of the drift pins or bolts buried in the connection and also because of the surface pressure effect at the abutment part of the beam and the column end surface. It is therefore possible to design the positioning of columns and bearing walls more freely, and to omit reinforcing members such as diagonal braces, knee braces, and angle braces. This eventually facilitates creation of a large-span space and an opening with a large frontage, and also enables creation of spaces where an upper-story column is not aligned with a lower-story column and is arranged over a columnless area in a lower floor.

The connection structure for glued laminated timber according to the present invention uses the pair of joint metals at the connection between the column and the beam, and connects the column and the beam via these joint metals by bolts or drift pins. This connection structure facilitates processing and assembly of the connection, ensures high processing accuracy, and can thereby reduce an on-site construction time.

It should be also noted that the medium or small dimension glued laminated timber for the column and the beam has excellent design property and gives a distinctive taste different from natural timber. The glued laminated timber may be exposed as the exterior and/or interior finish of a building, thereby creating a unique space featured by a combination of the warm texture and the firm and strong impression of the wooden material.

Further, the connection structure for glued laminated timber according to the present invention can reduce the depth of the slit formed in the column as compared to the conventional structure, and can easily form mortises in the beam. The present connection structure can thus cut the cost and labor required in slit processing or other like processes.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of a rigid frame made of glued laminated timber (hereinafter referred to as “glulam rigid frame”) according to a first embodiment of the present invention.

FIG. 2 is a top view of the glulam rigid frame.

FIG. 3 is a side view of the glulam rigid frame.

FIG. 4 is a partial front view of the glulam rigid frame, showing a column-to-beam connection on an enlarged scale.

FIG. 5 is a perspective view of a joint metal used at the column-to-beam connection in the glulam rigid frame.

FIG. 6 is a partial front view of a column-to-beam connection in a glulam rigid frame according to a second embodiment of the present invention.

FIG. 7 is a partial top view of the column-to-beam connection shown in FIG. 6 .

FIG. 8 is an exploded perspective view of a column-to-beam connection according to a third embodiment of the present invention.

FIG. 9 is a front view showing a connection in a conventional connection structure.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention are now described with reference to the drawings.

A connection structure for glued laminated timber according to the present invention is a connection structure at a column-to-beam connection in a glulam rigid frame that is a building frame based on the rigid frame structure. Columns and beams in this structure are each composed of a solid timber material of medium or small dimension glued laminated timber. The glued laminated timber construction method intended by the present invention can be achieved by combining a plurality of sets of glulam rigid frames.

Rigid frames may be combined suitably in accordance with the type of building. The rigid frames may have a flat portal shape, a pitched portal shape, a trapezoidal shape, etc., and may be single-story or multi-story.

FIGS. 1 to 5 illustrate the first embodiment of the present invention. FIG. 1 is a front view of a glulam rigid frame. FIG. 2 is a top view of the glulam rigid frame. FIG. 3 is a side view of the glulam rigid frame. FIG. 4 is a partial front view of the glulam rigid frame. FIG. 5 is a perspective view of a joint metal.

A glulam rigid frame 1, as illustrated, is a flat portal rigid frame in which the beam is connected on top of the columns, with a span of about 3 m. Posts 11 are solid timber materials of medium dimension glued laminated timber having a cross section of 105 mm (column thickness)×390 mm (column width). A beam 12 is a solid timber material of medium dimension glued laminated timber having a cross section of 105 mm (beam width)×390 mm (beam depth). Note that the columns 11 and the beam 12 are not limited to the above-mentioned cross-sectional dimensions. Small dimension glued laminated timber is applicable for a smaller span. A practical span is approximately up to 7 m.

The columns 11 and the beam 12 made of medium dimension glued laminated timber are rigidly connected to each other, using two joint metals 13 at each connection. Each joint metal 13 has a steel plate portion 131 and a steel pipe portion 133, respectively including fixing holes 132, 134 for drift pins or bolts. The plate portion 131 and the pipe portion 133 are integrated together by welding or otherwise to form the racket-like joint metal 13, with the pipe portion 133 extending coaxially with the plate portion 131 from a peripheral side of the plate portion 131. In this configuration, the fixing holes 132 penetrating the plate portion 131 and the fixing holes 134 penetrating the pipe portion 133 are oriented in the same direction.

At an end of each column 11, a slit 111 is formed to open at a column end surface and to extend in a column width direction (left-right direction in FIG. 1 ), and holes (not shown) having substantially the same diameter as the pipe portions 133 of the joint metals 13 are formed close to both ends of the slit 111. At an abutment part in the beam 12 that abuts on the column end surface, mortises 121 penetrating in a beam depth direction are formed at two positions that are appropriately spaced from each other in a span direction. The joint metals 13 have their pipe portions 133 fitted in the corresponding mortises 121 of the beam 12, and have their plate portions 131 fitted in the slit 111 of the column 11. For structural resistance, it is desirable to arrange the joint metals 13 close to both ends of the abutment part of the column 11 and the beam 12. The distance between the joint metals 13 is suitably determined in consideration of the column width and the size of the plate portions 131 of the joint metals 13. The joint metals 13 inserted across the column 11 and the beam 12 are integrally connected to the column 11 and the beam 12, by a plurality of drift pins 51 and bolts 52 inserted from a side surface (a front or back surface in FIG. 1 ) of the column 11 and the beam 12. The drift pins 51 and bolts 52 ensure the strength at the connection by their shear resistance (shear strength). In addition, the bolts 52 fastened with nuts serve to tighten the ends of the timber materials where the slit 111, the mortises 121, etc. are formed. Connecting the column 11 and the beam 12 via the two spaced joint metals 13 increases the resistance in rotational directions at the abutment part of the column 11 and the beam 12, thereby forming a strong glulam rigid frame 1 with a rigid connection between the column 11 and the beam 12.

In addition, an auxiliary metal 14 may be arranged between the spaced joint metals 13. The auxiliary metal 14 has, for example, a tubular shape having substantially the same diameter as the pipe portions 133 of the joint metals 13, or a flat plate-like shape having substantially the same thickness as the plate portions 131 of the joint metals 13. Fixing holes 141 for drift pins or bolts are provided at both ends of the auxiliary metal 14. The ends of the auxiliary metal 14, one being inserted in the slit 111 formed in the column 11, and the other being inserted in a slit or hole (not shown) formed in the beam 12, are secured by drift pins 51 or bolts 52 in the same manner as the joint metals 13.

Connecting the column 11 and the beam 12 by the combined use of the joint metals 13 and the auxiliary metal 14 increases the resistance in the shear directions at the abutment part of the column 11 and the beam 12.

Incidentally, a column and a beam may be connected by a conventional technique as shown in FIG. 9 , via a connecting plate 73 inserted entirely across the beam depth and the column width. This conventional technique requires, however, a large-diameter (about 1-m-diameter) circular saw to process a slit 711 for a column 71 and a slit 721 for a beam 72, and thus increases cost and labor. In contrast, the connection structure according to the present invention forms the slit 111 in the column end surface in a depth of about a half to one-third of the column width, and thus can use a small-diameter (up to about 30-cm-diameter) circular saw to process the slit. The slit of this depth practically ensures sufficient bonding strength and tenacity, and can be processed much more easily than in the conventional technique shown in FIG. 9 .

FIGS. 6 and 7 illustrate the second embodiment of the present invention. This embodiment is different from the first embodiment in the type of joint metals. The following description is focused on this difference and omits detailed description of the other elements by using the same reference signs.

Each joint metal 23 according to this embodiment has one plate portion 231 and two pipe portions 233. The pipe portions 233 are integrated with the plate portion 231, and extend parallel to each other from a peripheral side of the plate portion 231. The plate portion 231 is provided with a plurality of fixing holes 232. As shown in FIG. 6 , fixing holes 234 provided in the two pipe portions 233 are not aligned but staggered in height between the pipe portions 233.

Mortises 121 corresponding to the shape of the joint metals 23 are formed at the connection of the beam 12, two mortises each per position, at two positions that are spaced from each other by a predetermined distance in the span direction. Each joint metal 23 has its pipe portions 233 fitted in the corresponding mortises 121, and has its plate portion 231 fitted in the slit 111. Each joint metal 23 is then integrally connected to the column 11 and the beam 12 by a plurality of drift pins 51 or bolts 52 driven in from the side surface of the column 11 and the beam 12.

Additionally, each joint metal 23 according to this embodiment includes indentations 236 in the lower end of the pipe portions 233. The indentations 236 are thin elongated notches formed in the lower end on two sides (front and back sides) of each pipe portion 233. The purpose of the indentations 236 is to reduce the yield strength at the connection between the plate portion 231 and the pipe portions 233. When an excessive load acts on the connection between the column 11 and the beam 12, the indentations 236 serve to prevent cracking in the timber materials.

Similar to the first embodiment, this embodiment can process the slit 111 in the column 11 by using a small-diameter (up to about 30-cm-diameter) circular saw, and can thus facilitate the slit processing.

FIG. 8 is an exploded perspective view showing the third embodiment of the present invention. In the connection structure according to this embodiment, the beam 12 of the glulam rigid frame 1 is connected with an upright lower-story column 11 and an upright upper-story column 35 via a joint metal 33 and a connector plate 37.

Similar to the joint metal 13 described in the first embodiment, the joint metal 33 has a plate portion 331 and a pipe portion 333 integrated in a racket-like shape. In addition, a receiver portion 335 having a slit is provided at the other end of the pipe portion 333. A fixing hole 336 is formed at an end of the receiver portion 335, and allows the connector plate 37 to be connected to the receiver portion 335. The connector plate 37 is a flat piece having a plurality of fixing holes 371 for receiving drift pins 51, etc.

To connect the beam 12 and the columns 11, 35, the joint metal 33 has its pipe portion 333 inserted into the mortise 121 from a bottom surface side of the beam 12, and is fixed in the beam 12 by bolts 52 inserted from a side surface of the beam 12. The plate portion 331 and the lower end of the pipe portion 333 projecting from the bottom surface side of the beam 12 are then inserted into the slit 111 and the hole 112 formed in the upper end of the lower-story column 11, and are fixed in the column 11 by the drift pins 51 or bolts 52 inserted from the front or back surface of the column 11. Thereafter, the connector plate 37 is inserted from the top surface side of the beam 12 into the receiver portion 335 at the upper end of the pipe portion 333, so that the connector plate 37 is ready to engage with the upper-story column 35.

To erect the upper-story column 35 on the top surface of the beam 12, the connector plate 37 and the upper end of the pipe portion 333 projecting from the top surface side of the beam 12 are inserted into a slit 351 and a hole 352 formed at the lower end of the upper-story column 35. The pipe portion 333, the connector plate 37, and the column 35 are integrally fixed by drift pins 51 or bolts 52 fitted in from the front or back surface of the upper-story column 35. The upper column 35 and the lower column 11 are thus connected, with the beam 12 in-between.

As illustrated, a horizontal member 36 (e.g., a smaller beam) may be attached to the beam 12 via a connection metal 38. The connection metal 38 has a back plate 381 and a pair of side plates 382 orthogonal to the back plate 381. The back plate 381 is placed on the side surface of the beam 12 and fastened on the beam 12 by the bolts 52 for fixing the joint metal 33. The side plates 382 projecting sidewise from the beam 12 are inserted in slits 361 formed at an end of the horizontal member 36, and are connected with the horizontal member 36 by drift pins 51 or bolts 52 inserted from side surfaces of the horizontal member 36.

REFERENCE SIGNS LIST

-   11 column -   111 slit -   12 beam -   121 mortise -   13 joint metal -   131 plate portion -   132 fixing hole -   133 pipe portion -   134 fixing hole -   14 auxiliary metal -   37 connector plate -   51 drift pin -   52 bolt 

1. A connection structure for glued laminated timber, in which a column and a beam made of medium or small dimension glued laminated timber are rigidly connected by a pair of joint metals such that the beam is connected on top of the column, wherein each of the joint metals comprises a plate portion and a pipe portion that are joined together in a racket-like shape, each of the plate portion and the pipe portion having a fixing hole for a drift pin or a bolt, wherein the column is provided with a slit at an end thereof, the slit opening at a column end surface and extending in a column width direction, and the beam is provided with mortises at an abutment part thereof that abuts on the column end surface, the mortises penetrating in a beam depth direction and arranged at two positions that are appropriately spaced from each other in a span direction, and wherein the pair of joint metals is fixed in the column and the beam by having the pipe portion of each joint metal fitted in corresponding one of the mortises and by having the plate portion of each joint metal being fitted in the slit of the column, and thereby establishes rigid connection between the column and the beam.
 2. The connection structure for glued laminated timber according to claim 1, wherein an auxiliary metal having a first end and a second end is arranged in between the pair of joint metals, and wherein the first end of the auxiliary metal is fixed in the column by a drift pin or a bolt, and the second end of the auxiliary metal is fixed in the beam by a drift pin or a bolt.
 3. The connection structure for glued laminated timber according to claim 1, wherein each of the joint metals includes a plurality of pipe portions per plate portion, and the pipe portions extend parallel to each other from a peripheral side of the plate portion.
 4. The connection structure for glued laminated timber according to claim 1, wherein a flat connector plate is connected to the pipe portion of at least one of the pair of joint metals, on a top surface side of the beam that is connected to a lower-story column by the pair of joint metals, and wherein an upper-story column is erected on the beam by having the connector plate fitted in a slit formed at a lower end of the upper-story column. 